A front fork is used for suspending a front wheel of a saddle-type vehicle such as a bicycle, tricycle and the like and includes a pair of dampers supporting the front wheel and a suspension spring elastically supporting a vehicle body by urging the dampers in an extending direction. In the front fork, as illustrated in FIG. 6, a damping characteristic (a change in a damping force with respect to a piston speed) is preferably constituted such that an extension-side damping force obtained by synthesis of the both dampers is relatively higher than a compression-side damping force. By employing such characteristic, a pushing-up input can be relaxed by a low compression-side damping force, and a high extension-side damping force can be exerted in the subsequent extension stroke, and vibration of a sprung member and an unsprung member can be quickly converged.
Dampers used for automobiles include a magnetic viscous fluid damper using a magnetic viscous fluid as a working fluid. For example, as illustrated in FIG. 7, a magnetic viscous fluid damper DC disclosed in JP2008-12959A is set as a single cylinder type and includes a cylindrical cylinder 100, a piston rod 200 going into/out of the cylinder 100, piston 300 held at a distal end of the piston rod 200 and defining a rod-side chamber r1 and a piston-side chamber r2 formed in the cylinder 100, a piston passage L1 formed in the piston 300 and allowing the rod-side chamber r1 and the piston-side chamber r2 to communicate with each other, a gas chamber r3 formed in the cylinder 100 and compensating for a change of an in-cylinder capacity for a piston rod mass going into/out of the cylinder 100, and a free piston 400 in sliding contact with an inner peripheral surface of the cylinder 100 and defining the piston-side chamber r2 and the gas chamber r3, and the magnetic viscous fluid as the working fluid is filled in the rod-side chamber r1 and the piston-side chamber r2, while a compressed gas is sealed in the gas chamber r3.
The magnetic viscous fluid damper DC includes viscosity adjusting means V6 for adjusting viscosity of the magnetic viscous fluid passing through the piston passage L1. The viscosity adjusting means V6 is composed of a coil provided on the piston 300 and conducting means for conducting electricity to the coil. When an electric current is made to flow through the coil by the conducting means, a magnetic field is generated in the piston passage L1, and the viscosity of the magnetic viscous fluid flowing through the piston passage L1 can be adjusted. The damping force generated when the magnetic viscous fluid damper DC is extended/contracted is caused by resistance when the magnetic viscous fluid in the chamber pressurized by the piston 300 moves to the other chamber through the piston passage L1. Since the resistance is changed in accordance with the viscosity of the magnetic viscous fluid, the damping force of the magnetic viscous fluid damper DC can be adjusted by the viscosity adjusting means V6.